Simple, when they refuse to say or explain the price, I truly lose all trust or faith in their opinion; I feel they are trying to maneuver me into buy an expensive tour. Money and travel are connected at the hip, it is impossible to disconnect.

Does the Lonely Planet Guidebook tell me the prices?
Yes

Does the Rough Guide tell me the prices?
Does Footprints Guidebooks tell me the prices?
Yes, yes and more yes.

There is a reason they sell many guidebooks, because they accept there is a connection between the word travel and the price.